FIG. 1 is a view provided to explain an approach route of an aircraft.
An aircraft has to navigate along a predetermined approach route, while maintaining a predetermined glide angle along a centerline of a runway as illustrated in FIG. 1 to land on the runway safely, and an aircraft landing support facility aids the aircraft to do so. The example of the aircraft landing support facility includes the Instrument Landing System (ILS), the Ground-based Augmentation System (GBAS), the Microwave Landing System (MLS), and so on.
The ground equipment of each of these systems is installed at airport and radiates predetermined signals so that a receiver mounted on an aircraft approaching the airport receives the signals and generates landing guidance information to guide runway approach and landing by referring to the received signals. The generated landing guidance information is provided to a pilot through the aircraft instrument such as the course deviation indicator (CDI) or the primary flight display (PFD), and so on, and the pilot refers to such information as he or she conducts safe runway landing flight.
The ILS has been in use from the 1050. As a landing support facility that has been used for the longest time, the ILS provides guaranteed reliability, and most of the world's airports are using the ILS as the landing support facility. Meanwhile, the ILS has decreased accuracy in the landing guidance information (i.e., lateral and vertical deviation information) than those provided by GBAS or MLS, and also has a disadvantage of increased cost as it requires that equipment be installed per runway to provide the landing guidance information.
The MLS has been installed and used at some airports in the 1990, but has not been installed and operated actively on a global scale. Among the three landing support facility (i.e., ILS, GBAS, MLS), MLS provides the second-greatest accuracy of the landing guidance information, and has the advantage of being operated independently without being influenced by jamming. However, a few airports installed MLS, and like the case of ILS, MLS also has the shortcoming of low economic feasibility as it requires equipment be installed per runway.
The GBAS has been installed and operated since 2009 in countries including Germany, United States, Australia, Spain, and so on, and its supply is currently increased worldwide. Among the three landing support facilities, the GBAS provides the greatest accuracy of the landing guidance information, and is also economic as it can provide landing guidance information about the entire runways in the airport with only one GBAS ground equipment installed at the airport. Possibly the only shortcoming of the GBAS would be associated with the use of GPS signals, since when GPS signals have jamming, then it may not be possible to use the GBAS. Except for the jamming, the GBAS provides far greater accuracy of the landing guidance information, and thus, more and more airports around the world that installed ILS are currently installing the GBAS additionally, and there is an increasing number of airports in the world that install both ILS and GBAS.
The methods and principles of respective systems for generating landing guidance information vary. However, there are mainly three common things in receiving signals from respective systems at a receiver mounted on an aircraft and finally generating the landing guidance information.
FIG. 2 is a view provided to explain landing support information of an aircraft.
Referring to FIG. 2, the ‘lateral deviation’ refers to a degree of deviation of an aircraft from a centerline of a runway to the left/right. The ILS can provide the difference in depth of modulation (DDM), which is a unit expressing the lateral deviation as a difference in the depth of modulation of a radio wave, calculate the lateral deviation basically in a distance unit (i.e., meter), and can also transform into DDM unit and angular unit and provide the same. The MLS can basically calculate the lateral deviation in an angular unit (i.e., degree), and can also transform the lateral deviation expressed in the angular unit into DDM unit and provide the same.
The ‘vertical deviation’ refers to a degree of deviation of an aircraft above/below the Glide Path Angle (GPA). The unit of the vertical deviation provided by respective landing support facilities is same as the vertical deviation unit described above.
Both the GBAS and MLS can continuously provide ‘distance to threshold’, meaning distance between aircraft and runway threshold, in a length unit of a lateral distance between the aircraft and the runway threshold. The ILS can determine a distance between aircraft and runway threshold only when the aircraft passes the points where the marker beacons are installed, and this distance determination is only possible within approximately 8 km distance from runway threshold and for three times.
The conventional multi-mode receiver (MMR) is an aviation electronic equipment that generates landing guidance information and aircraft navigation information necessary for the aircraft to land on the runway, and MMR is mounted on the aircraft.
FIG. 3 is a view provided to explain a conventional MMR.
Referring to FIG. 3, the current large-scale civil aircrafts have the MMR of the structure illustrated in FIG. 3 mounted thereon to receive signals transmitted from the ground equipment of respective landing support facilities and generate landing guidance information, so that the generated information is provided to a pilot through the aircraft instrument (e.g., CDI, PFD, and so on).
Due to expensive cost of the aircraft landing supporting facilities, not every airport installs ILS, MLS and GBAS in view of economic aspect. Most airports basically install ILS, and certain (about 10) airports outside Korea install MLS on a trial basis, but use thereof was not extended and is almost died out. The GBAS, having far greater performance than ILS, has been installed from the 2009 in airports of many countries of the world (e.g., United States, Germany, Spain, Australia, Swiss, Korea, and so on), and approximately 40 airports of the world have completed installation or currently installing it. Among these, USA's Huston Airport, Newark Airport, Australia's Sydney Airport, Germany's Bremen Airport, Frankfurt Airport, and Spain's Malaga Airport are currently providing commercial services, and Korea has also installed GBAS at the Gimpo Airport and is operating it on a trial basis. Since the GBAS is installed on a trial basis at the airports having ILS already installed therein, these airports allow runway landing using ILS and also allow landing using GBAS. The airports installed with MLS can also allow aircrafts to conduct runway landing by using ILS and MLS, respectively.
Because most airports do not install all of the landing support facilities, a purchaser of the currently-available MMR can purchase desired processors as the options, by selecting from among the MLS processor 106, the ILS processor 107, and the GBAS processor 108 as exemplified in a receiver 105 of FIG. 3. Generally, the GNSS processor 109 in the receiver 109 is basically mounted.
The landing mode selector 110 receives from a flight management system (FMS) 111 the information on landing support facility to be used during landing of an aircraft, transmits an instruction to generate landing guidance information to one of the MLS processor 106, the ILS processor 107, and the GBAS processor 108, and receives the landing guidance information generated at a corresponding processor and transmits this back to the FMS 111.
When a pilot selects only the ILS processor 107 and the GBAS processor 108 through the FMS 111, the aircraft mounted with the corresponding MMR is able to land by using the corresponding landing support facility of the airport installed with the ILS or GBAS. Meanwhile, when only the ILS processor 107 and the MLS processor 106 are selected, the corresponding MMR is able to land only on the airport installed with the ILS or MLS.
Meanwhile, the conventional MMR includes all of the ILS processor 107, the GBAS processor 108, and the MLS processor 106 therein, and even when the airport is installed with all of the ILS, GBAS, and MLS, landing guidance information provided by only one landing support facility corresponding to the landing mode selected by the FMS 111 during aircraft landing is generated, and the generated information is provided to the aircraft instrument. That is, it is so designed that the pilots land by using only one landing support facility during runway landing.
Accordingly, when the GBAS ground equipment is out of order or when GPS jamming occurs while the aircraft attempting a runway landing with GBAS is about 10 NM (nautical mile) from runway threshold, the conventional MMR is not able to provide successive landing guidance information. Therefore, the aircraft is not able to land, but has to go around and then fly back to the initial approach fix which is about 20 NM away from the runway to make additional landing attempt. In this case, aircraft fuel consumption increases, and aircraft landing time is also delayed. Even if the pilot determines that the GBAS landing guidance information signals are lost and thus changes into ILS mode, about several seconds are necessary until ILS landing guidance information is outputted. Considering high velocity of an aircraft which can move a considerable distance even in a brief time, if the above-described circumstance occurs at a near distance to the runway, the aircraft will not be able to change mode, but has to go around and fly back.